With development of big data and cloud computing, a capacity of optical switching at a data center is increasing day by day, and demands for a scale and a speed of an optical switch array are increasing accordingly. A silicon-based optical switch process is compatible with a mature Complementary Metal Oxide Semiconductor (CMOS) process, and a silicon-based optical switch has advantages such as low costs and high integration. Therefore, it is easy to implement a large-scale optical switch array. In addition, under a thermo-optic effect of a silicon material, a switching speed of an optical switch may reach an order of microseconds. For example, a 32×32 silicon-based interferometric thermal optical switch is described in a paper “Ultra-compact 32×32 strictly-non-blocking Si-wire optical switch with fan-out LGA interposer” in Optics Express, vol. 23, no. 13, #240124, June 2015, and a switching time of the 32×32 silicon-based interferometric thermal optical switch is 30 microseconds. However, as a driving power increases, signal light of such an interferometric optical switch unit that is based on a Mach Zehnder Interferometer (MZI) structure is periodically output alternately at two ports. In addition, due to a process error, an initial state of the interferometric optical switch unit is random. Therefore, operating points of switching states of the optical switch unit need to be determined one by one. Usually, an integrated optical detector is used to determine the operating point. This increases control difficulty substantially, and limits application of the interferometric optical switch unit.
A switching state of a digital optical switch is a stable state. That is, as a driving power increases, signal light is output from only one port, instead of being periodically output alternately at two ports as in an interferometric device. Process tolerance is high, and control difficulty is low. However, the thermo-optic effect of the silicon material is relatively weak, and therefore a large temperature difference cannot be obtained by using a traditional heating method, and an effective refractive index change caused is only 0.001. As a result, a component required for implementing the silicon-based optical switch is very long (usually on an order of centimeters), and a loss is relatively large. This is unfavorable to integration of a large-scale silicon-based optical switch array. Therefore, it is important in a future all-optical switching technology to implement a silicon-based optical switch with high heating efficiency, a compact structure, and a low insertion loss.